Browser Address Book as Firefox Addon

The new Contacts addon creates an address book in Firefox that provides access to local and remote friends and buddies. The special aspect of the addon is that it's controlled by the browser and the browser determines which application or website can access the contact. The Firefox extension also provides autocompletion of contact email addresses in forms, for example.

The integrated address book is especially useful for autocompleting email addresses in forms.

According to Mozilla Lab's announcement in their blog, the Contacts addon is still in an experimental stage and currently supports contact synchronization with GMail, Twitter and the Mac OS X address book only. However, a generic importer tool already allows bringing in contacts from desktop or Web-based sources.